Phthalocyanine Moiety Research Articles

Synthesis and photophysical properties of novel phthalocyanine–perylenediimide–phthalocyanine triad and phthalocyanine–perylenediimide dyads

Three novel multi-component chromophores based on phthalocyanine and perylenediimide moieties were synthesized by one condensation reaction.

Synthesis and properties of novel polymeric metal-free and metallophthalocyanines containing peripherally long 1,2-bis[(3-oxapropyl)oxa]benzene derivatives

New polymeric phthalocyanine moieties (M = 2H, Zn, Ni, Cu, and Co) were synthesized via polytetracyclomerization reaction of o-bis[3-(3,4-dicyanophenoxy)propyloxy]benzene (3), which can be obtained by the reaction of 4-nitrophthalonitrile with o-bis[(3-hydroxypropyl)oxy]benzene. Aggregation and disaggregation behavior of the polymeric phthalocyanine (5) was studied with some alkali and earth alkali metal cations. Measured intrinsic viscosities of the polymeric phthalocyanines exhibited a substantial decreasing tendency with dilution of the solution. Thermogravimetric analysis was performed under air by using DSC and DTG/TGA techniques and indicated that these polymers have good thermal stability. AC and DC electrical conductivities of the polymeric phthalocyanines were investigated in the frequency range 100 Hz--1 MHz within the temperature range 298--343 K. AC/DC conductivities of the samples were found to be between 10-5 and 10-7 S cm-1 at ambient temperature under argon atmosphere. The structures of new synthesized compounds were characterized by using microanalysis; various spectroscopic methods such as UV-Vis, FT-IR, 1H NMR, and 13C NMR spectroscopy; and MS spectra.

Octaoctyl-Substituted Lutetium Bisphthalocyanine for NADH Biosensing

Cyclic voltammetric and Raman and UV-vis spectroscopic measurements were performed on thin films of nonperipherally substituted bis[1,4,8,11,15,18,22,25-octakis(octyl)phthalocyaninato] lutetium(III) (R16LuPc2). Voltammograms exhibit one-electron quasi-reversible redox processes in 1.5 M LiClO4 aqueous solutions. The red-shift of the Q-band of R16LuPc2 in the UV-visible absorption spectra upon oxidation is attributed to the shortening of the inter-ring distance between the two phthalocyanine moieties. This observation is also consistent with the shift in the redox-sensitive vibrational modes in the Raman spectra due to the localization of the positive charge on phthalocyanine moieties. Neutralization of the oxidized R16LuPc2(+) film by dihydronicotinamide adenine dinucleotide (NADH) using different concentrations varying from 0.05 to 1 mM has been studied by UV-vis absorption and Raman spectroscopies. The reduction processes for a three month old film were found to be slower than those for freshly prepared films and showed a dependence upon NADH concentration. The data provide a basis for application of R16LuPc2 as a sensor for NADH.

Chirality induction in binuclear phthalocyanine tweezers

A novel binuclear phthalocyanine tweezers, in which two zinc-phthalocyanine rings are linked to an optically active binaphthyl group through triazolyl linkages, was self-cyclized through triazolyl-to-zinc coordination bonds. An axially chiral S-binaphthyl group induced planar chirality in a slipped-cofacial stack of phthalocyanine moieties, and therefore displayed fluorescence with a good quantum yield (ΦF=0.23) and circularly polarized luminescence with a moderate intensity of dissymmetry factor (glum=−4×10−4) in the near-infrared wavelength region.

Photophysical properties of anthracenylmethyloxycarbonylmethylsulfanyl-phthalocyanines

Metal-free and metallophthalocyanine compounds with four 9-anthracenylmethyl ester of thioglycolic acid groups have been prepared via esterification of related carboxy-terminated derivatives of phthalocyanines with anthracene-9-methanol. In order to justify the esterification reaction, UV–vis spectra have been used as an efficient tool: in addition to the usual Q and B bands of phthalocyanine moieties, the presence of anthracene groups was proven with their strong absorptions in the range of 340-380nm. Aggregation tendency of the newly prepared Pcs has been investigated in the concentration range of 1.0-5.0×10−6M. The influence of the substituents and the metal ions on the spectroscopic and photophysical properties of the Pcs has been investigated. The energy transfer to phthalocyanine core and radiative decays of the anthracene emission and phthalocyanine core were examined. The lower energy transfer efficiency is probably due to the saturated linker moiety and lack of spectral overlap between phthalocyanine core and anthracene units.

Synthesis of (zinc(II) phthalocyanine)-containing cellulose derivative using phthalocyanine-ring formation reaction

2,3-Di-O-myristyl-6-O-(zinc(II) phthalocyaninyl) cellulose (5) was synthesized from cellulose (1) by five reaction steps via 6-O-(3′,4′-dicyanophenyl)-2,3-di-O-myristyl cellulose (4). The key reaction was phthalocyanine-ring formation on a cellulose backbone, that is, the reaction of compound 4 with o-phthalodinitrile in the presence of hexamethyldisilazane and zinc acetate in DMF afforded to compound 5 in 35.4 % yield. Consequently, the degree of substitution with phthalocyanine moieties of compound 5 was 0.38. The LB monolayer film of compound 5 on an indium tin oxide (ITO) electrode was found to show photocurrent generation performance at 680 nm.

Metallophthalocyanine and Metallophthalocyanine–fullerene complexes as potential dye sensitizers for solar cells DFT and TD-DFT calculations

The geometries, electronic structures, polarizabilities and hyperpolarizabilities, and UV–vis spectra of metallophthalocyanine dyes and metallophthalocyanine–fullerene supramolecules are investigated by using density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. The results reveal that the metal and the tertiary butyl groups of the dyes are electron donors, and the phthalocyanine rings are electron acceptors. The electron donating power of (La) is significantly greater than that of (Sc). For dyes, the highest occupied molecular orbitals (HOMOs) are π orbitals localized over the phthalocyanine rings, away from the tertiary butyl groups, and the lowest unoccupied molecular orbitals (LUMOs) are π∗ orbitals localized over the central metal atoms. The HOMOs of the dyes fall within the (TiO2)60 and Ti38O76 band gaps, and support the issue of typical interfacial electron transfer reaction. The resulting potential drop of the supramolecule LaPc.C60 increases by ca. 22.86% under the effect of the tertiary butyl groups. This significant increase in the potential drop indicates that the tertiary butyl complexes could be a better choice for the robust operation of the molecular rectifiers. The introduction of metal atom and tertiary butyl groups to the phthalocyanine moiety leads to a stronger response to the external electric field, and induces higher photo-to-current conversion efficiency. This also shifts the absorption in the dyes and makes them potential candidates for harvesting light in the entire visible and near IR region for photovoltaic applications. It is also observed that the high spin state complex Sc(4)Pc could not be a potential candidate for harvesting light in the former region of spectrum.

Photodynamic therapy potential of thiol-stabilized CdTe quantum dot-group 3A phthalocyanine conjugates (QD-Pc)

Thiol stabilized CdTe quantum dot (QD) nanoparticles were synthesized in aqueous phase and were used as energy donors to tetra-triethyleneoxythia substituted aluminum, gallium and indium phthalocyanines through fluorescence resonance energy transfer (FRET). Energy transfer occurred from the QDs to phthalocyanines upon photoexcitation of the QDs. An enhancement in efficiency of energy transfer with the nature of the carboxylic thiol stabilizer on the QDs was observed. As a result of the nanoparticle and the phthalocyanine mixing, the photoluminescence efficiency of the phthalocyanine moieties in the mixtures does not strictly follow the quantum yields of the bare phthalocyanines. The photochemistry study of phthalocyanines in the presence of the QDs revealed high singlet oxygen quantum yield, hence the possibility of using QDs in combination with phthalocyanines as photosensitizers in photodynamic therapy of cancer. The fluorescence of the CdTe quantum dots-phthalocyanine conjugates (QDs-Pc) were effectively quenched by addition of 1,4-benzoquinone.

Side chain polysiloxanes with phthalocyanine moieties

Side chain polysiloxane with 5-(pentyloxy)-3-methyloxy-9,10,16,17,23,24-hexakis(octenyloxy)phthalocyanine moieties is synthesized by hydrosilylation reaction. The phase behavior and thermooptical properties of the polysiloxane and starting 2-(pent-4-enyloxy)-3-methyloxy-9,10,16,17,23,24-hexakis(octenyloxy)phthalocyanine is examined by POM (Polarizing optical microscopy), TOA (thermooptical analysis), DSC (differential scanning calorimetry), AFM (atomic force microscopy) and SAXS (small angle X-ray scattering) studies. The effect of the attachment of phthalocyanine to polysiloxane chains over phase transitions and phase morphology is discussed in details.

Sequential energy and charge transfer processes in mixed host–guest complexes of subphthalocyanine, porphyrin and phthalocyanine chromophores

Porphyrins, phthalocyanines and subphthalocyanines are three attractive classes of chromophores with intriguing properties making them suitable for the design of artificial photosynthetic systems. The assembly of these components by a supramolecular approach is of particular interest as it provides a facile means to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. In this paper, we show the formation of mixed host-guest supramolecular complexes that consist of a β-cyclodextrin-conjugated subphthalocyanine, a tetrasulfonated porphyrin and a series of silicon(IV) phthalocyanines substituted axially with two β-cyclodextrins via different spacers. We found that the three components form supramolecular complexes held by host-guest interactions in aqueous solution. Upon excitation of the subphthalocyanine part of the complex, the excitation energy is delivered to the phthalocyanine unit via excitation energy transfer and the porphyrin chromophore acts as an energy transfer bridge enabling this process. It was shown that photo-induced charge transfer also takes place. A sequential electron transfer process from the porphyrin unit to the phthalocyanine moiety and subsequently from the subphthalocyanine moiety to the porphyrin unit takes place, and the probability of this process is controlled by the linker between β-cyclodextrin and phthalocyanine. The lifetime of the charge-separated state was found to be 1.7 ns by transient absorption spectroscopy.

Tetra(β-phenothiazinyl) zinc phthalocyanine: An easily prepared D 4–A system for efficient photoinduced electron transfer

Four identical electron donor (D) moieties, phenothiazines (PTZs), were covalently attached onto the same acceptor (A), zinc phthalocyanine (ZnPc), to form ZnPc(β-PTZ) 4, i.e. D 4–A. The symmetrical D 4–A was synthesized by the condensation method to examine intra-molecular photoinduced electron transfer (PET). The common electron donor-spacer–acceptor (D–A) photosynthetic models, which involve the asymmetrical synthesis of a mono-substituted porphyrin or its analogs, suffer from a low yield and arduous isolation, since D–A is only one of several products (D n –A or A n –D, n = 0, 2–4). The D 4–A preparation, however, can be carried out without the problem. The steady state and time-resolved fluorescence of the D 4–A were measured and compared with that of ZnPc(β-R) 4 (R = H, OPh). The result showed that the excited singlet state of phthalocyanine moiety in the D 4–A molecule was efficiently quenched by phenothiazine units owing to intra-molecular PET. The rate constant of PET ( k et) was calculated and the value is much higher than the rate constant of fluorescence emission, intersystem crossing and internal conversion of ZnPc moiety. The laser flash photolysis study revealed the presence of a long-lived charge-separated state due to PET. The results suggest that a D 4–A system can be a more efficient artificial photosynthetic model than D–A towards the practical commercial use.

Photoinduced electron transfer (PET) within D 4–A and D–A photosynthetic systems: Enhanced intramolecular PET achieved by increasing the number of donors

Photoinduced electron transfer (PET) occurring within D 4 – A was compared to that within D– A, in which A (electron acceptor) was a single zinc phthalocyanine moiety and D (electron donor) a phenothiazine unit, using UV–vis absorption, fluorescence emission and laser flash photolysis. D and A in both models were directly linked by covalent C–N bonds. The symmetrical D 4 – A system, for which both the synthesis and purification were more straigthforward than for D– A, displayed a much faster PET rate constant; although the D– A system was more difficult to prepare, it exhibited less efficient PET. The charge separation state formed through PET showed long lifetimes on the μs scale in the cases of both the D 4 – A and D– A molecules.

The Role of Fe in the Preparation of Carbon Alloy Cathode Catalysts

Pyrolysis of iron phthalocyanine/phenolic resin (FePc/PhRs) and phthtalocyanine/phenolic resin (Pc/PhRs) was studied to clarify the effect of Fe during the preparation of carbon alloy cathode catalysts. FePc/PhRs pyrolyzed at 600° showed the best electrocatalytic activity for oxygen reduction. CHN elemental analysis suggests that the catalysts with higher nitrogen content tend to show better catalytic activities. The results of TG/DTA/MS and IR suggest that Fe increases the nitrogen content of the catalysts by enhancing the interaction of phthalocyanine moiety and phenolic resin.

Preparation and Optical Limiting Properties of Multiwalled Carbon Nanotubes with π-Conjugated Metal-Free Phthalocyanine Moieties

Phthalocyanines (Pcs) usually exhibit stronger optical limiting response that can be used to protect human eyes, optical elements, and sensors from intense laser pulses. New unsymmetrically substituted metal-free phthalocyanine-covalently functionalized multiwalled carbon nanotubes (PcH2-MWNTs), in which the wt % of MWNTs in the resulting product was found to be 35%, were synthesized. A considerably quenching of the fluorescence intensity was found in the photoluminescence spectrum of PcH2-MWNTs. This observation suggests a quenching of the singlet excited PcH2 by the covalently linked MWNTs. This material exhibits strong scattering at higher intensities, which evidently comes from the MWNT counterpart. The nonlinear response of tBu3NH2PcH2 is due to reverse saturable absorption (RSA), while that of PcH2-MWNTs is due to both RSA and nonlinear scattering, which could be two conflicted mechanisms for optical limiting, giving rise to suppression of the whole nonlinear response of PcH2-MWNTs.

Coordination-induced sliding motion of a complementary porphyrin-phthalocyanine dimer: fluorescence-based molecular switch

The reversible control of dual (or multiple) states of molecules and supramolecules has attracted much attention for molecular switch, sensor, memory, logic gate, and molecular machine applications. In this paper, a ligand-induced sliding system using a complementary porphyrin-phthalocyanine dimer accompanied by a large fluorescence change is described. An imidazole-appended porphyrinatozinc-phthalocyaninatomagnesium complex 5 was synthesized by the palladium-catalyzed coupling reaction of the corresponding porphyrin and phthalocyanine moieties. The imidazole group of 5 coordinated to the magnesium ion of another 5 was formed spontaneously and dominantly to give a stacked dimer 5ST in non-coordinating solvents, such as chloroform, even at submicromolar concentration (< 10-6 M). When an appropriate amount of dimethyl sulfoxide (DMSO) was added to the 5ST solution, the stacked dimer was transformed almost quantitatively into the extended dimer 5Ex. This transformation was monitored by UV-vis and fluorescence spectroscopies. In the UV-vis spectra, the porphyrin's Soret band is split characteristically because of excitonic coupling between the two closely located porphyrins in 5Ex. At the same time, the fluorescence intensity of 5Ex at 700 nm (ex. 414 nm) increased by a factor of 28 compared with that of 5ST. Removal of the DMSO molecules by extraction with water from the system regenerated 5ST almost completely from 5Ex, and the fluorescence was quenched again. The reversible system can be repeated by cycles of addition and removal of DMSO. The present system can be classified as a coordination-induced sliding system accompanied by a large fluorescence change, and may be applied as a fluorescence-based molecular switch.

Synthesis, structural investigation and thermal stability of 2-aminoethanolo-κ- O-magnesium(II) phthalocyanine 2-aminoethanol solvate

2-Aminoethanolo-κ- O-magnesium(II) phthalocyanine 2-aminoethanol (2AE) solvate was obtained and its crystal structure was determined by single-crystal X-ray diffraction technique that has shown two molecules in the asymmetric unit. The Mg atom is 4+1 coordinated by isoindole N atoms of phthalocyaninate(2-) ring and by O atom of 2AE molecule in axial position. The last is hydrogen bonded with the solvate 2AE molecule. The phthalocyanine moieties are non-planar, the deviation of Mg(II) atom from the plane of four N-isoindole atoms is equal to ∼0.5 Å. The crystal packing shows the formation of back-to-back π–π stacked dimers of MgPc molecules, which form the channels, occupied by hydrogen bonded ligand molecules. Thermal studies of MgPc(2AE)·(2AE) revealed two-stage mass loss at 165 and 215 °C, which correspond to the loss of hydrogen bonded and coordinated 2AE molecules, respectively, and lead to the β-form of MgPc.

Exciplex Mediated Photoinduced Electron Transfer Reactions of Phthalocyanine-Fullerene Dyads

Evidences of an intramolecular exciplex intermediate in a photoinduced electron transfer (ET) reaction of double-linked free-base and zinc phthalocyanine-C60 dyads were found. This was the first time for a dyad with phthalocyanine donor. Excitation of the phthalocyanine moiety of the dyads results in rapid ET from phthalocyanine to fullerene via an exciplex state in both polar and nonpolar solvents. Relaxation of the charge-separated (CS) state Pc(*+)-C60(*-) in a polar solvent occurs directly to the ground state in 30-70 ps. In a nonpolar solvent, roughly 20% of the molecules undergo transition from the CS state to phthalocyanine triplet state (3)Pc*-C60 before relaxation to the ground state. Formation of the CS state was confirmed with electron spin resonance measurements at low temperature in both polar and nonpolar solvent. Reaction schemes for the photoinduced ET reactions of the dyads were completed with rate constants obtained from the time-resolved absorption and emission measurements and with state energies obtained from the fluorescence, phosphorescence, and voltammetric measurements.

Photoinduced Electron Transfer in Langmuir−Blodgett Monolayers of Double-Linked Phthalocyanine−Fullerene Dyads

Photoinduced electron transfer (ET) in films of the double-linked free-base phthalocyanine−fullerene dyads (Pc−C60) was studied in solid Langmuir−Blodgett (LB) films using femtosecond pump−probe and microsecond flash-photolysis methods. Excitation of the phthalocyanine (Pc) moiety of the dyad results in a rapid (0.8 ps) intramolecular ET from phthalocyanine to fullerene. The formed charge separated (CS) state relaxes in 35 ps, yielding an intermolecular CS state, which relaxes to the ground state in the microsecond time domain. The surface organization of the Pc−C60 dyad monolayers was studied by atomic force microscopy for both pure Pc−C60 films and Pc−C60 mixed films with matrix molecules, octadecylamine (ODA). This study together with the estimations done based on surface pressure−mean molecular area isotherms reveals that the dyads tend to aggregate rather than form a homogeneous mixture with the ODA molecules. This enforces intermolecular interactions and leads to the formation of a long-lived intermolecular CS state.

Synthesis and anchoring of antineoplastic ferrocene and phthalocyanine derivatives on water-soluble polymeric drug carriers derived from lysine and aspartic Acid.

The general synthetic strategy towards water-soluble biodegradable drug carriers and the properties that they must have are discussed. The syntheses of water-soluble biodegradable copolymers of lysine and aspartic acid as potential drug-delivering devices, having amine-functionalised side chains are then described. Covalent anchoring of carboxylic acid derivatives of the antineoplastic ferrocene and photodynamically active phthalocyanine moieties to the amine-containing drug carrier copolymers under mild coupling conditions has been achieved utilising the coupling reagent O-benzotriazolyl-N,N,N′,N′-tetramethyluronium hexafluorophosphate to promote formation of the biodegradable amide bond. Even though the parent antineoplastic ferrocene and phthalocyanine derivatives are themselves insoluble in water at pH 7, the new carrier-drug conjugates that were obtained are well water-soluble.

Synthesis of diiodo butadiynyl-bridged bisphthalocyaninatozinc(II) complexes

Two functionalized phthalocyanine-based chromophore systems having two iodophthalocyaninatozinc(II) rings bound together through a butadiynyl linkage 1a, b have been synthesized by oxidative Eglinton coupling of the corresponding monomer, and fully characterized. The electronic characteristics of these extensively linearly π-conjugated compounds were modulated by the introduction of different peripheral substituents into the phthalocyanine moieties and investigated by UV–visible spectroscopy. The reactivity of the two iodo substituents was explored to prepare a novel bisphthalocyanine containing two ethynylphenyl moieties, thus pointing out the possibility of incorporating other electro and/or photoactive moieties in the BisPc system, taking advantage of the iodo-functionalization.